/*******************************************************************************************
 * Copyright (c) 2006-2009 Alex Robson, Rob Simmons, Craig Israel, and Rachel Twyford
 *
 * Use of this software in any form requires that you have both 
 * read and agreed to the following terms:
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the "Software"), 
 * to deal in the Software without restriction, including without limitation 
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 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions: 
 *
 * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
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 * this list of conditions and the following disclaimer in the 
 * documentation and/or other materials provided with the distribution.
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using System.Collections.Generic;
using System.Linq;
using Nvigorate.Data.Query;
using Nvigorate.Extensions;
using Nvigorate.Relational.Builders;
using Nvigorate.Relational.Mapping.Index;
using Nvigorate.Relational.Repository;

namespace Nvigorate.Relational.Visitors
{
    public class DeleteVisitor : IPersistableVisitor
    {
        protected IRepositoryMapIndex _repositoryMapIndex;
        protected List<object> _visited = new List<object>();
        protected QueryList _queryResult = new QueryList();
        protected bool _recursive;
        protected IPersistable _root;

        /// <summary>
        /// Build a delete query for the provided object.
        /// </summary>
        /// <param name="persistable">The object to build the query for.</param>
        /// <param name="parent">The parent object of the persistable</param>
        /// <remarks>The parent argument is not used in this visitor.</remarks>
        public void Visit(IPersistable persistable, IPersistable parent)
        {
            if (Visited(persistable))
                return;

            if (_root == null)
                _root = persistable;

            _visited.Add(persistable.Instance);

            var targetType = persistable.InstanceType;

            // if something's not mapped, don't try to delete it (seems obvious, right?)
            if (_repositoryMapIndex.HasMap(targetType) && _repositoryMapIndex.CanDelete(targetType))
            {
                var bindingMap = _repositoryMapIndex.GetMap(targetType);

                bindingMap
                    .GetSourceMapsInCreateOrder(true)
                    .Where(s => s.CanDelete)
                    .Select(s => new DeleteBuilder(s, persistable))
                    .ForEach(b => _queryResult.Add(b.Build()));
            }
        }

        public bool Visited(IPersistable persistable)
        {
            return _visited.Exists(i => ReferenceEquals(i, persistable.Instance));
        }

        public TraversalDirection Direction
        {
            get { return _recursive ? TraversalDirection.DepthFirst : TraversalDirection.NoTraversal; }
        }

        public QueryList GetQuery()
        {
            IQueryObject removeRelationships = GetRemoveRelationships();
            return new QueryList() {removeRelationships, _queryResult};
        }

        protected IQueryObject GetRemoveRelationships()
        {
            var manyToManyVisitor = new ManyToManyRelationshipVisitor(new PersistenceKeyManager(_repositoryMapIndex), _repositoryMapIndex,
                                                                      Operation.Delete);
            _root.GetNavigator(_repositoryMapIndex).Accept(manyToManyVisitor);
            return manyToManyVisitor.GetQuery();
        }

        public DeleteVisitor(IRepositoryMapIndex mapIndex, bool recursive)
        {
            _repositoryMapIndex = mapIndex;
            _recursive = recursive;
        }
    }
}